1. Field of the Invention
This invention relates to swash plate type compressors used in the refrigeration cycle of air conditioning systems for motor vehicles, for example, and more particularly it is concerned with a silencer structure for the compressor of the type described which has the effect of removing within the compressor the pulsations of pressure of a refrigerant in a gaseous state under high pressure that is compressed by and discharged from the compressor.
2. Description of the Prior Art
A swash plate type compressor comprises a rotary shaft and a swash plate secured to the rotary shaft which moves in swinging movement as the rotary shaft rotates. The rotary shaft is journaled by a cylinder block and disposed coaxially with the center line of the cylinder block which is formed with a plurality of cylinder bores disposed parallel to the rotary shaft for receiving pistons for sliding movement therein.
The pistons are connected to the swash plate through a mechanism for converting the swinging movement of the swash plate into a reciprocatory movement of the pistons, so that rotation of the rotary shaft causes the pistons to move in reciprocatory movement in the cylinder bores. The cylinder block has a side cover mounted at one end portion thereof with a valve plate being interposed between the side plate and the cylinder block. A space enclosed by the side cover and valve plate is divided into a low pressure chamber and a high pressure chamber. The low pressure chamber and high pressure chambers are both maintained in communication with the cylinder bores via suction and discharge valves mounted on the front and rear surfaces of the valve plate.
As the pistons move within the cylinder bores in a direction in which they move away from the valve plate, the volume of the cylinder bores increases and the refrigerant is drawn into the cylinder bores from the low pressure chamber via the suction valves. Conversely, as the piston moves within the cylinder bores in a direction in which they move toward the valve plate, the volume of the cylinder bores decreases and the refrigerant is discharged through the discharge valves into the high pressure chamber while being compressed. The refrigerant compressed in the cylinder bores is successively discharged from the cylinder bores and introduced into the high pressure chamber, so that the pressure in the high pressure chamber increases each time the compressed refrigerant is introduced thereinto from each cylinder bore.
The refrigerant in a compressed state delivered by the compressor to the refrigeration cycle produces pulsations of pressure of the same number as the cylinder bores while the rotary shaft makes one complete revolution.
U.S. Pat. No. 3,712,759 (U.S. Ser. No. 103,412 of Jan. 4, 1971; Inventor, John W. Olson, Jr.) and U.S. Pat. No. 3,904,320 (U.S. Ser. No. 358,334 of May 8, 1973; Inventors, Kishi et al.) each disclose a swash plate type compressor. The compressor disclosed in the former is what is generally referred to as a single side swash plate type compressor in which seven bores are formed at one side of the swash plate, and the compressor disclosed in the latter is what is generally referred to as a double side swash plate type compressor in which three bores are formed at either side of the swash plate or six bores in total are formed at both sides of the swash plate.
In the former type compressor, seven pressure peaks are produced in a high pressure chamber in a side cover during one complete revolution of the swash plate. In the latter type compressor, the refrigerant compressed in the three bores at one side of the swash plate is directly discharged from the bores into a high pressure chamber formed in a side cover at the side from which the refrigerant is drawn off. The refrigerant compressed in the three bores at the other side of the swash plate is first discharged from the bores into a high pressure chamber formed in another side cover at the other side from which the refrigerant is led through a communication passage to the high pressure chamber formed in the side cover at the side from which the refrigerant is drawn off. Thus in the latter type compressor, six pressure peaks are produced in the high pressure chamber formed in the side cover at the side from which the refrigerant is drawn off while the swash plate makes one complete revolution.
The refrigerant compressed in the compressor of the swash plate type and supplied to the refrigerant cycle produces pulsations of pressure of a basic frequency of n.times.m wherein n is the number of revolutions of the swash plate and m is the number of the cylinder bores. When the refrigerant directly delivered to the refrigeration cycle has the aforesaid pulsations of pressure, the component parts of the refrigeration cycle, including a condenser, pipes and an evaporator, are caused to vibrate. This would produce noises or cause damage to welds formed in the component parts of the refrigeration cycle.
To avoid these disadvantages, a proposal has been made, first of all, to provide a silencer in a pipe connecting the compressor to the condenser as an independent member.
Secondly, in a compressor of the double side swash plate type, a proposal has been made, as disclosed in U.S. Pat. No. 3,577,891 (U.S. Ser. No. 851,687 of Aug. 20, 1969; inventor, Tani), to utilize as silencing chambers the spaces of the segmental cross-sectional shape formed between the bores of the cylinder blocks.
Thirdly, a proposal has been made, as disclosed in Japanese Utility Model Application Laid-Open Number 44313/75 (Application No. 97708/73; Application Date, Aug. 20, 1973; Inventor; Yamada et al.), to provide a silencing chamber at one side of the side cover for drawing off the compressed refrigerant through the silencing chamber.
Fourthly, a proposal has been made in U.S. Ser. No. 950,573 of Oct. 12, 1978 (inventor, Kishi), now U.S. Pat. No. 4,274,813, to partition the high pressure chamber within the side cover into over two chambers by partition plates arranged axially thereof.
Some disadvantages are associated with all the silencer structures of the prior art. The silencer structure of the first proposal requires an additional pipe for connecting the silencer to the compressor and condenser, and there is the risk of the refrigerant leaking through the connections. In the silencer structure of the second proposal, the diameter of the compressor becomes large, and special means should be provided for shielding from atmosphere a refrigerant passage formed at the outer periphery of the compressor. Additionally, a special silencing should be used because no satisfactory results are obtained in reducing noises in spite of the volume being large in this silencer structure. In the third proposal, a construction for sealing the silencing chamber to shield same from atmosphere should be provided. There is the risk of the refrigerant leaking through the sealing construction. In the silencer structure of the fourth proposal, difficulties have been encountered in providing the silencing chamber with a necessary volume, so that satisfactory silencing effects have been hard to achieve.